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ab7e209d1b
This allows running *any* read-only query with mt_dop > 0. Before this patch, no joins were allowed with mt_dop > 0. Previous patches, particularly IMPALA-9156, added significantly more code coverage for multithreading+joins. It should be safe to allow enabling on a query-by-query basis. Many improvements are still planned - see IMPALA-3902. So behaviour and performance characteristics of mt_dop > 0 with more complex plans and joins will continue to change. Testing: Updated the mt_dop validation tests and remove redundant planner test that doesn't provide much additional coverage of the validation support. Ran exhaustive tests. Change-Id: I9c6566abb239db0e775f2beaa25a62c36313cd6f Reviewed-on: http://gerrit.cloudera.org:8080/15545 Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com> Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>